JP2010142848A - Brazing method and brazing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brazing method in which the brazing strength between a fitting object such as a circuit board with an object to be fitted such as an electronic component to be mounted thereon is high even when a lead-free solder is used, its dispersion is less, the secular change of the brazing strength is less, and the reliability is high for a long time, and a brazing apparatus employing the brazing method. <P>SOLUTION: In the brazing method for executing the brazing by heating and melting a lead-free brazing filler metal, a cooling step of the heated and molten brazing filler metal is controlled in time-temperature while applying the ultrasonic wave thereto. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brazing method for performing lead-free soldering using an electric iron or the like, and a brazing apparatus employing this brazing method, for example.

In recent years, when joining with a brazing material containing solder from the viewpoint of environmental problems, for example, when joining electrical and electronic components to a wiring board, lead-free solder, specifically, for example, , Sn-Ag and Sn-Cu compositions are used as the main component.
By the way, in joining using a brazing material, it is difficult to perform the joining work because various physical and chemical events such as the wettability and composition of the brazing material and the heat resistance of the wiring board and mounted components are involved. Or a high bonding strength cannot be obtained, or the reliability of the bonded portion decreases with time.
In addition, the flux used to activate the joint surface and increase the joint strength may cause problems such as corrosion and deterioration of the working environment.
In particular, these problems are different from conventional Pb—Sn solder, and lead-free solder has a short history. Therefore, the cause has not been fully elucidated, and it will be a major problem to be solved in the future.

Originally, this type of brazing involves melting and liquidizing the brazing material and bringing it into contact with the surface of a connection part (hereinafter simply referred to as a pad) such as a wiring board, and intermetallic compounds due to the brazing material and the composition components of the pad on the surface layer. It is said that good bonding strength and long-term reliability can be obtained by forming and further refining and uniformly dispersing the crystal grains of the brazing filler metal and the intermetallic compound.
In this regard, the Pb—Sn solder that has been used in the past is refined and uniformly dispersed in the brazing filler metal and the intermetallic compound crystal grains with relatively no problem due to Pb, and has good joint strength and long-term reliability. Was obtained.

However, when the brazing material was changed to lead-free solder, brazing was attempted in the same way as the conventional Pb-Sn solder, but the lead-free brazing material was difficult to melt and difficult to join, so the joint strength was insufficient. As a result, there have been problems that sufficient bonding strength cannot be obtained, or that bonding strength decreases with time even after bonding.
Specifically, a typical lead-free solder, for example, Sn-Ag solder will be described. This Sn—Ag solder has a melting temperature higher by about 40 ° C. to 50 ° C. than the conventional Pb—Sn solder, and as a result, there is no thermal margin for the wiring board and the electronic components mounted thereon. Therefore, in order to lower the melting temperature and bring it close to the melting temperature similar to that of the conventional Pb—Sn solder, for example, a metal having a so-called melting point lowering action (hereinafter referred to as a melting point lowering action metal) such as Bi (bismuth) or In (indium). ) May be added.

However, when Bi or In, which is a melting point lowering metal, is added to Sn-Ag solder, the temperature range from the melted state to solidification is widened compared to conventional Pb-Sn eutectic solder, During solidification, a state in which a part where Bi or In, which is a melting point lowering metal, is partially solidified and a part still in a molten state occurs, so-called segregation of crystal grains is likely to occur.
As described above, as a result of adding the melting point lowering metal Bi or In to lower the melting temperature, segregation is likely to occur. This segregation causes enlargement of crystal grains and non-uniform dispersion, and the bonding strength is not stabilized. There is a problem that long-term reliability cannot be obtained.

  Therefore, as disclosed in Patent Document 1, for example, when an electronic component is to be brazed to a pad of a wiring board with lead-free solder, for example, Bi that is a melting point lowering metal is heated and melted. In the process of cooling the added Sn-Ag solder, a minute vibration such as an ultrasonic wave is added to the solder to prevent segregation of Bi crystal grains at the bonding interface between the wiring board and the electronic component. Proposals have been made to improve the bonding strength between the wiring board and the electronic component by miniaturizing and uniformly dispersing Bi crystal grains.

JP 2000-351063 A

In the invention disclosed in Patent Document 1, the applicant argues as follows.
That is, for example, in the cooling process of a Sn-Ag lead-free solder in which a melting point lowering metal Bi is added, by applying ultrasonic waves to this, the surface tension of the solder is lowered and the flow is improved. That is, wettability can be improved.
As a result, it is possible to prevent segregation of Bi crystal grains at the bonding interface between the wiring board and the electronic component, and to realize finer and uniform dispersion of Bi crystal grains, thereby improving the bonding strength between the wiring board and the electronic component. Insist that you can.

When using an Sn-Ag solder to which Bi is added as in Patent Document 1 and ultrasonic waves are applied in the solder cooling process, the junction between the wiring board and the electronic component is more effective than the conventional method. An alloy layer of copper (Cu) and tin (Sn) can be surely formed at the bonding interface of, and, for example, when melting point depressing metal Bi is added, segregation of Bi crystal grains is effectively prevented. It is possible to improve the bonding strength.
However, from the viewpoint of certainty, there is still not enough. Specifically, there is a variation in the bonding strength, and it has not yet reached a point where it is possible to reliably ensure improved bonding strength and long-term reliability of the bonded portion.

  As a result of studying the cause, the present inventor has determined that the hot air from the hot air generator 201 is applied to the electronic component 205 in such an experimental apparatus configuration in the first to sixth lines of paragraph number 0033 of Patent Document 1. The lead-free solder 122 was melted, and after the melting, the hot air was stopped and naturally cooled to solidify the lead-free solder 122. The ultrasonic wave generated by the ultrasonic transmitter 202 was simultaneously with the start of the natural cooling. Attention was focused on the description "The action has started."

In general, in the process of crystallization progressing from the molten state to solidification, the segregation, refinement or uniform dispersion of crystal grains should depend on the cooling conditions.
Therefore, as described above in Patent Document 1, in the cooling process of lead-free solder in a molten state, regardless of the composition of lead-free solder, how to apply ultrasonic waves simply by natural cooling Even so, it was speculated that the necessary joint strength could not be obtained stably.
At the same time, the problem is not limited to the precipitation state of the crystal grains of the melting point lowering metal. For example, in the case of Sn-Ag solder, in order to obtain a stable bonding strength, the main component of Sn crystal grains It was also considered that refinement and uniform dispersion should be more important than refinement and uniform dispersion of crystal grains of melting point lowering metals such as Bi, which are only additives.

Actually, when the electronic component was brazed (soldered) to the wiring board using Sn-3.5Ag solder (not including a metal having a melting point lowering effect such as Bi) by the method described in Patent Document 1. Although the intermetallic compound of copper and Sn was surely formed on the copper surface on the wiring board side, focusing on the size and uniform dispersion of Sn crystal grains, some of the Sn crystals are It was difficult to say that the dispersion was uniform.
From the above, the inventor of the present invention has found that the main component of lead-free solder is Sn, and, for example, when a melting point lowering metal is added thereto, In order to reliably realize miniaturization and uniform dispersion, and to obtain stable high bonding strength and long-term reliability, it is necessary to optimize the cooling conditions according to the composition of the lead-free solder, The present invention has been reached.

  In view of the above problems, an object of the present invention is to improve the bonding strength between a mounted object such as a wiring board and a mounted object such as an electronic component mounted thereon even when lead-free solder is used. It is an object of the present invention to provide a brazing method that can reduce the variation of the bonding strength over time, that is, has little variation, that is, has a long-term reliability, and a brazing apparatus that employs this brazing method.

In order to achieve the above object, a brazing method according to claim 1 of the present invention is a brazing method in which lead-free brazing material is heated and melted and brazing is performed. However, it is characterized by time-temperature control.
According to the brazing method of claim 1 thus formed, in the cooling process of the lead-free brazing material heated and melted, cooling is performed while applying ultrasonic waves and controlling the time-temperature relationship. For example, when an electronic component is mounted on a wiring board using Sn-Ag solder to which Bi, which is a melting point lowering metal, is added, the crystallization of Sn and Bi at the joint is less segregated and the like. It is possible to proceed under optimum crystallization conditions in which the crystal grains are finer and the distribution thereof is uniform.
As a result, it is possible to effectively prevent, for example, segregation of Sn and Bi at a joint portion between a mounting object such as a wiring board and a mounting object such as an electronic component mounted on the mounting object, thereby increasing the bonding strength. In addition, it is possible to obtain a joint with little variation and excellent long-term reliability.

[Claim 1]
In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
A brazing device having a function of increasing the peel strength of brazing.

[Claim 2]
In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
Reduce the diameter of the crystal particles of the brazing material that has been cooled and solidified,
And / or
By homogenizing the dispersion of crystal particle diameters,
A brazing device having a function of increasing the peel strength of brazing.

[Claim 3]
In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
Reduce the number of voids per unit volume in the cooled and solidified brazing material,
And / or
By reducing the average diameter of the voids,
A brazing device having a function of increasing the peel strength of brazing.

[Claim 4]
In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
By improving the wetting properties of the molten brazing material on the surface of the brazing material,
A brazing device having a function of increasing the peel strength of brazing.

[Claim 5]
In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
A brazing material surface;
At the interface with the brazing material in the molten state and / or the cooled and solidified state,
By forming an alloy layer of brazing material and brazing material,
A brazing apparatus having a function of increasing the peel strength of brazing.

[Claim 6]
The brazing material is a lead-free brazing material,
The brazing apparatus according to any one of claims 1 to 6.

  In the invention of the present application, a lead-free brazing material is heated and melted, and brazing is performed in the brazing apparatus for performing brazing. -Brazing method characterized by temperature control.

  The invention of the present application is a brazing method characterized by not using a flux.

  In the invention of the present application, the temperature of the molten brazing material is measured by a temperature sensor and the temperature of the surface of the brazing material is measured from the temperature or from the outside, and the cooling process of the molten brazing material is exceeded. It is a brazing method characterized by time-temperature control while applying sound waves.

  The invention of the present application is characterized in that brazing is characterized in that the cooling process is time-temperature controlled while applying ultrasonic waves by cooling the ambient atmosphere of the molten brazing material using a temperature-controlled cooling medium. Is the method.

  The invention of the present application is a brazing method characterized by surrounding the periphery of the molten brazing material and cooling the atmosphere inside the brazing material using a temperature-controlled cooling medium.

  The invention of the present application is characterized in that a lead-free brazing material is heated and melted using an electric iron having a built-in ultrasonic generation source, and the cooling process is time-temperature controlled while applying ultrasonic waves. This is how to braze.

  In the invention of the present application, the electric iron has a temperature sensor at a tip portion thereof, and the cooling process of the molten brazing material is applied with ultrasonic waves according to the temperature measured by the temperature sensor while applying time to temperature. It is the brazing method characterized by controlling.

  The invention of the present application is a brazing method characterized in that the electric iron has a cooling medium discharge port at a tip portion thereof.

  The invention of the present application is a brazing apparatus that heats and melts a lead-free brazing material, and ultrasonically controls the cooling process of the heat-melted brazing material with time-temperature control while applying ultrasonic waves. A brazing device comprising a generator and a time-temperature control device.

  The invention of the present application is a brazing device characterized in that the brazing device is an electric iron.

  The invention of the present application has a metal body that generates Joule heat when the tip portion of the electric iron is excited by the electromagnetic induction coil, and an electromagnetic induction coil is formed on an outer periphery of the tip portion. The brazing apparatus is characterized in that an electric wire having a heat resistance of 400 ° C. or higher is used as the electric wire forming the electromagnetic induction coil.

  The invention of the present application is a brazing apparatus characterized in that the heat-resistant electric wire is obtained by applying a heat-resistant insulating coating to a copper conductor.

  The invention of the present application is a brazing device characterized in that a portion of the electromagnetic induction coil is covered with a heat-resistant coating material.

  The invention of the present application is a brazing apparatus characterized in that the heat-resistant coating material is glass, ceramics or beryllium oxide.

  In the invention of the present application, the tip of the electric iron is made of copper plated with iron or iron / nickel, or made of iron or iron / nickel with a hollow inside and a shell-shaped outer shape. It is the brazing apparatus characterized by this.

  The invention of this application is the tip of the electric iron, and an intermetallic compound layer of copper and iron or copper and nickel is formed at the boundary between copper and iron plating or iron / nickel plating covering the copper. It is the brazing apparatus characterized by being made.

  The invention of the present application is a brazing device characterized in that the electric iron has a cooling medium discharge port for discharging a temperature-controlled cooling medium at a tip portion thereof.

  In the invention of the present application, the tip portion of the electric iron and the ultrasonic wave generation source are linearly arranged via a horn member, and heat insulation is provided between the tip portion and the ultrasonic wave generation source. A brazing device characterized in that a member is interposed.

  The invention of the present application is that the ultrasonic generator has an ultrasonic generation source and a horn member that transmits vibration generated by the ultrasonic generation source to the tip portion, and the horn member has heat insulation properties. This is a brazing device.

  The invention of the present application is a brazing device in which the heat insulating member and the heat-insulating horn member are made of titanium, stainless steel, glass, porcelain, or a combination thereof.

  The invention of the present application is a brazing device characterized in that the tip portion of the electric iron has a resonance frequency correction function for generating a plurality of resonance frequencies.

  The brazing method according to the invention of the present application is preferably characterized in that no flux is used.

  According to the brazing method according to the invention of the present application, wettability can be improved by applying ultrasonic waves, and accordingly, no flux is used. As a result, flux does not remain in the joint. Therefore, it is possible to eliminate the possibility that the joint portion deteriorates with time due to the flux residue, and it is possible to further improve the long-term reliability. Moreover, deterioration of the working environment due to vaporization of the flux can be prevented.

In a preferred embodiment of the brazing method according to the invention of the present application, the temperature of the molten brazing material is measured by a temperature sensor and the temperature is measured from the temperature or the surface temperature of the brazing material is measured from the outside. It is characterized by time-temperature control of the brazing filler metal cooling process while applying ultrasonic waves.
For example, a temperature sensor is attached to the tip of an electric iron and inserted into a molten brazing material, and the temperature is measured directly, or the value measured near the molten brazing material is indirectly approximated. Or by measuring the surface temperature of the molten brazing material from the outside with an infrared temperature measuring instrument, etc., and using any of these obtained temperatures, the cooling process of the molten brazing material is exceeded. Time-temperature control while applying sound waves.
In this way, it becomes possible to control the time-temperature of the cooling process of the molten brazing material with high accuracy while applying ultrasonic waves.
As a result, it is possible to obtain a bonded portion using lead-free solder, which has a higher bonding strength, less variation, and excellent long-term reliability.

In a preferred embodiment of the brazing method according to the invention of the present application, the cooling step is cooled using a temperature-controlled cooling medium to cool the ambient atmosphere of the molten brazing material while applying ultrasonic waves to the time-temperature. It is characterized by control.
In a preferred embodiment of the brazing method according to the invention of the present application, a cooling medium whose temperature is controlled by the time-temperature control of the brazing material cooling process, specifically, an inert gas such as nitrogen or argon or water is misted. Since a cooling medium having a temperature controlled in advance is used, the cooling process of the molten brazing material can be time-controlled while applying ultrasonic waves with good responsiveness.
In this way, the process of cooling the molten brazing material can be time-temperature controlled with high accuracy and easily, with higher bonding strength and less variation, and long-term reliability. An excellent joint can be obtained.

In a preferred embodiment of the brazing method according to the invention of the present application, the periphery of the molten brazing material is enclosed, and the atmosphere inside the brazing material is cooled using a temperature-controlled cooling medium. .
In a preferred embodiment of the brazing method according to the invention of the present application, it is only necessary to enclose the periphery of the molten brazing material and control the temperature of only the atmosphere inside the molten brazing material. It can be performed more quickly and accurately. Further, since the cooling range is narrowed, there is an effect that the amount of cooling gas used, for example, a cooling gas such as argon gas can be reduced.

In a preferred embodiment of the brazing method according to the invention of the present application, a lead-free brazing material is heated and melted using an electric iron containing an ultrasonic generation source therein, and the cooling step is performed while applying ultrasonic waves. It is characterized by time-temperature control.
In a preferred embodiment of the brazing method according to the invention of the present application, since the brazing method described above can be realized by a compacted electric iron, for example, by giving this electric iron to the hand of a robot or the like, It becomes possible to apply the brazing method of the present invention to various fields.

In a preferred embodiment of the brazing method according to the invention of the present application, the electric iron has a temperature sensor at a tip thereof, and the step of cooling the molten brazing material according to the temperature measured by the temperature sensor. Is characterized by time-temperature control while applying ultrasonic waves.
In a preferred embodiment of the brazing method according to the invention of the present application, since the temperature sensor is provided at the tip of the electric iron closest to the molten solder, the temperature of the molten brazing material is directly or indirectly determined. Measurement can be performed at a position very close to the molten brazing material.
As a result, the time-temperature control in the cooling process of the molten brazing material can be performed with higher accuracy.

In a preferred aspect of the brazing method according to the invention of the present application, the electric iron has a cooling medium discharge port at a tip portion thereof.
In a preferred embodiment of the brazing method according to the invention of the present application, since the electric iron has a cooling medium discharge port at the tip thereof, when cooling the brazing material in a molten state, from an extremely close position, For example, a cooling medium such as a temperature-controlled cooling gas or cooling mist can be discharged. Therefore, the molten brazing material can be cooled with good responsiveness, and the time-temperature control in the cooling process of the molten brazing material can be performed with higher accuracy.

In a preferred embodiment of the brazing apparatus according to the invention of the present application, a brazing apparatus for performing heat-melting of a lead-free brazing material while applying ultrasonic waves to the cooling process of the heat-melted brazing material. It is characterized by comprising an ultrasonic generator for time-temperature control and a time-temperature control device.
In a preferred embodiment of the brazing device according to the invention of the present application, since it has an ultrasonic generator and a time-temperature control device, in the cooling process of the molten brazing material, the addition of ultrasonic waves Since time-temperature control can be performed together, it is possible to effectively prevent segregation of melting point lowering metals such as Sn, Bi, and I, which are solder main components, in the joint, and there is little segregation of Sn, Bi, or I. In addition, crystals with fine crystal grains and a uniform distribution can be reliably deposited.
That is, it is possible to improve the bonding strength of the bonded portion more reliably, reduce the variation thereof, and obtain long-term reliability.

In a preferred embodiment of the brazing device according to the invention of the present application, the brazing device is an electric iron.
In a preferred embodiment of the brazing device according to the invention of the present application, the brazing device is a convenient tool such as an electric iron, so that it can be easily mounted on, for example, a robot and is convenient.

In a preferred embodiment of the brazing device according to the invention of the present application, the tip portion of the electric iron has a metal body that is excited by an electromagnetic induction coil and generates Joule heat, and on the outer periphery of the tip portion. Is characterized in that an electromagnetic induction coil is formed, and an electric wire having heat resistance of 400 ° C. or higher is used as the electric wire forming the electromagnetic induction coil.
In a preferred embodiment of the brazing device according to the invention of the present application, the tip portion of the electric iron is excited by a so-called electromagnetic induction coil in which a coating layer made of a magnetic material such as iron plating is applied to copper. It is made of a metal body that generates heat, and the outer periphery of the tip is 400 ° C., which is much higher than around 230 ° C., which is the melting temperature of lead-free solder, as an electromagnetic induction coil for generating Joule heat at the tip. Since the electromagnetic induction coil is formed by winding the electric wire having the above heat resistance, the electric wire is not easily deteriorated even if the tip of the electric iron is heated to a high temperature. Therefore, when lead-free solder is heated and melted, the tip of the electric iron can be instantaneously heated above the melting temperature of lead-free solder with peace of mind.

In a preferred aspect of the brazing apparatus according to the invention of the present application, the heat-resistant electric wire is a copper conductor provided with a heat-resistant insulating coating.
As described above, as a heat-resistant electric wire used in the present invention, a copper conductor is provided with a heat-resistant insulating coating, specifically, a heat-resistant insulating coating formed by, for example, wrapping glass tape or coating alumina. Therefore, heat resistance of 400 ° C. or higher can be reliably realized.

In a preferred aspect of the brazing device according to the invention of the present application, the portion of the electromagnetic induction coil is characterized in that its surface is covered with a heat-resistant coating material, and the heat-resistant coating material is glass, It is a ceramic or beryllium oxide.
In a preferred embodiment of the brazing device according to the invention of the present application, the entire surface of the part of the electromagnetic induction coil, that is, the part around which the heat-resistant electric wire is wound is covered with a heat-resistant coating material such as glass or ceramics. By this, the electric wire which is a heater for heating can be reliably and easily fixed firmly to the tip of the electric iron.
Moreover, since the surface of the electric wire can be prevented from being oxidized with this heat-resistant coating material, the heat resistance of the electric wire can be assisted and its life can be extended.

  In a preferred embodiment of the brazing apparatus according to the invention of the present application, the tip of the electric iron is made of copper plated with iron or iron / nickel, or made of iron or iron / nickel and has an internal cavity and an outer shape. Is in the shape of a shell, and at the tip of the electric iron, copper and iron at the boundary between copper and iron plating or iron / nickel plating covering the copper Alternatively, an intermetallic compound layer of copper and nickel is formed.

In a preferred embodiment of the brazing device according to the invention of the present application, the tip of the electric iron is made of copper plated with a magnetic material such as iron plating or iron / nickel plating, or iron or iron / nickel. It is made of a magnetic material that has a hollow interior and a bullet-shaped outer shape, so it has excellent heat generation, and it has an iron-plated or iron / nickel-plated coating layer on the surface, or iron or iron / nickel. This is a member having a hollow inside and a bullet-like outer shape, and can prevent copper (Cu) inside the tip from being corroded by tin (Sn) on the lead-free solder side. Therefore, the life of the tip of the electric iron can be extended.
Moreover, since an intermetallic compound layer of copper and iron or copper and nickel is formed at the boundary between copper and iron plating or iron / nickel plating that covers the copper, between copper and iron plating or between copper and iron / nickel plating The adhesive strength of the steel becomes high, the coating layer by plating is difficult to peel off, the life of the electric iron tip 7 can be extended, and the thermal conductivity to the inner copper body is also stabilized over a long period of time. You can also.

In a preferred aspect of the brazing device according to the invention of the present application, the electric iron has a cooling medium discharge port for discharging a temperature-controlled cooling medium at a tip portion thereof. is there.
In a preferred embodiment of the brazing device according to the invention of the present application, a cooling medium such as a temperature-controlled inert gas or mist-like water is supplied from a cooling medium discharge port formed at the tip of the electric iron. Since it can be discharged, the temperature of the lead-free solder in a molten state can be controlled at an extremely close position. Therefore, the time-temperature control when cooling the molten lead-free solder can be performed with higher accuracy.

In a preferred embodiment of the brazing device according to the invention of the present application, the tip portion of the electric iron and the ultrasonic wave generation source are arranged linearly via a horn member, and the tip portion and the supersonic wave source are arranged. A heat insulating member is interposed between the sound wave generation sources.
In a preferred embodiment of the brazing device according to the invention of the present application, the tip of the electric iron and the ultrasonic wave generation source are arranged in a straight line via the horn member. I can tell the department reliably. In addition, since a heat insulating member is interposed between the tip portion and the ultrasonic wave generation source, specifically, since the heat insulating material is interposed in the end surface portion of the horn member or in the middle thereof, it is heated. The adverse effect of the heat of the tip on the ultrasonic wave generation source can be reduced.

In a preferred embodiment of the brazing device according to the invention of the present application, the ultrasonic generator has an ultrasonic generator and a horn member that transmits vibration generated by the ultrasonic generator to the tip. The horn member has a heat insulating property.
In the preferred embodiment of the brazing device according to the invention of the present application, since the entire horn member is formed of a heat insulating material, the adverse effect of the heat of the heated tip on the ultrasonic wave generation source is minimized. Can do.

In a preferred aspect of the brazing device according to the invention of the present application, the heat insulating member and the horn member having heat insulating properties are made of titanium, stainless steel, glass, porcelain, or a combination thereof.
In a preferred embodiment of the brazing device according to the invention of the present application, a horn member that transmits ultrasonic waves from an ultrasonic wave generation source such as a heat insulating member or a piezoelectric element to a tip portion of an electric iron is a material having excellent heat insulating properties. Since it is composed of titanium, stainless steel, glass, porcelain, or a combination thereof, the heat of the tip of the electric iron, which is the heater, is less likely to have an adverse effect on the ultrasonic wave generation source. As a result, the thermal effect on the ultrasonic characteristics can be further eliminated.

In a preferred embodiment of the brazing device according to the invention of the present application, the tip portion of the electric iron has a resonance frequency correction function for generating a plurality of resonance frequencies.
In a preferred embodiment of the brazing device according to the invention of the present application, the tip of the electric iron is provided with a groove or a protrusion, or several tips of different materials are prepared and can be replaced at any time. Therefore, even if the type of lead-free solder to be used changes, it is possible to create an optimal resonance frequency for the solder.
Even if the heat of the tip of the electric iron affects the horn member that constitutes the ultrasonic generator, the deviation of the resonance point due to the temperature change can be corrected. It is also possible to eliminate the thermal effects.

  As described above, according to the present invention, even when lead-free solder is used, for example, the bonding strength between an attachment such as a wiring board and an attachment such as an electronic component mounted thereon can be increased, and It is possible to provide a brazing method and a brazing apparatus adopting this brazing method that can reduce the variation and have a long-term reliability with little change in bonding strength over time.

Embodiments of a brazing method of the present invention and a brazing apparatus employing the brazing method will be described in detail below with reference to the drawings.
FIG. 1 is a partially sectional schematic front view of a main part showing an embodiment of an electric iron, specifically, a brazing apparatus used for carrying out the brazing method of the present invention, and FIG. FIG. 2 is an enlarged partial cross-sectional view (only a part of the tip is a non-cross-sectional view).
As described above, a part of both FIGS. 1 and 2 is a cross-sectional view for easy understanding of the internal configuration. Further, the meaning of referring to FIG. 1 as a partial cross-sectional schematic front view of the main part is that the exterior part of the electric iron is removed and only the main part inside is shown.
As shown in FIG. 1, at the rear end of the electric iron 1, the piezoelectric elements 2 and 2 that are ultrasonic wave generation sources are in contact with each other so that their polarities are-, +, +, and-. The surfaces are stacked so as to be in close contact with each other, and these are firmly fixed to the horn member 3 with screws 4. Here, reference numeral 5 denotes a pressing member provided as necessary.
The horn member 3 has a cross-section reducing portion 6 whose cross section is gradually narrowed from the right side to the left side so that the left end face in FIG. 1 is smaller than the contact area of the contact surface with the piezoelectric element 2. Have.

Here, when the contact area of the horn member 3 with the piezoelectric element 2 is S ₁ and the cross-sectional area of the left end face 3 a of the horn member 3 is S ₂ , the end face increases as the value of S ₂ / S ₁ is decreased. The amplitude of the ultrasonic wave in 3a can be increased.
That is, the reason why the cross-section reducing portion 6 described above is provided is to make the amplitude of the ultrasonic wave added to the molten solder described later larger than the amplitude of the ultrasonic wave generated by the piezoelectric element 2.
Further, the front end portion 7 (heater portion) of the electric iron 1 is screwed to the left side of the horn member 3, and the male screw 8 at the rear end of the front end portion 7 screwed at this time is connected to the horn member 3. Screwed into a female screw 9 formed on the left end face 3a.

By the way, the end surface 3a of the horn member 3 and the end surface of the fixing portion 10 on the side of the tip portion 7 that contacts the end surface 3a so that the ultrasonic wave can be accurately transmitted from the horn member 3 to the tip portion 7 of the electric iron 1 without characteristic change. 11 may be brought into surface contact in an extremely dense state. Therefore, the end face 3a and the end face 11 are preferably formed to have the same outer shape, and both surfaces that are in contact with each other are processed into a mirror finish.
Incidentally, it goes without saying that the relationship between the male screw 8 and the female screw 9 may be reversed, that is, the positional relationship between the male screw and the female screw may be reversed.

The electric iron 1 shown in FIGS. 1 and 2 employs an electromagnetic induction heater. Therefore, on the left side of the fixed portion 10 provided at the distal end portion 7 of the electric iron 1, an electric wire 13 having a heat resistance of, for example, 400 ° C. or more is wound around about 20 turns, and the electromagnetic induction coil 14 is formed. Is formed. This electric wire 13 is a heat-resistant electric wire, and the surface of the copper conductor is covered with a glass material or an alumina material, which is an insulating coating material excellent in heat resistance, and its heat-resistant characteristics are increased to 400 ° C. or higher.
Further, between the electromagnetic induction coil 14 and the surface of the tip portion 7, a heat-resistant seat 14a made of glass fiber or alumina fiber, which is an excellent heat-resistant insulating material, is formed into a tape or a braid, for example. .
Further, a heat-resistant coating layer 14b made of glass, ceramics, beryllium oxide or the like is applied on the electromagnetic induction coil 14 so that the electromagnetic induction coil 14 is firmly fixed to the tip 7 of the electric iron 1.
The heat-resistant seat 14a and the heat-resistant coating layer 14b are not always necessary and can be omitted.

As shown in FIG. 2, the tip 7 located inside the electromagnetic induction coil 14 that is induction-heated by the electromagnetic induction coil 14 has a main body 17 made of copper or beryllium oxide, which is made of iron plating or iron / nickel plating. The coating layer 18 having a thickness of about 100 mμ is applied.
As a result, the coating layer 18 is excited by induction heating to generate Joule heat, and the tip portion 7 can be efficiently heated. Further, by adopting the electromagnetic induction method, the tip portion 7 can be reduced in size, and therefore the heat capacity of the tip portion 7 as a whole can be reduced. As a result, there is also an advantage that the tip 7 can be heated to a predetermined temperature in a short time.
Further, the provision of the coating layer 18 can effectively prevent the copper body 17 from being corroded by tin (Sn), which is one of the solder-side compositions, due to the difference in ionization tendency. .

  Further, a cooling medium discharge port 15 having an inner diameter of 1.0 mm or less is provided at a more distal portion of the electric iron 1, specifically, at a position about 2 mm from the front end. For example, an inert gas such as nitrogen gas or argon gas heated to a predetermined temperature, that is, temperature-controlled, or mist-like water or the like is flowed, and the tip which is a heater portion of the electric iron 1 The section 7 can be cooled accurately along a predetermined pattern of time-temperature control described later.

A temperature sensor 16 is also attached at a position within 2 mm from the tip of the tip 7. In this way, at the position closest to the molten lead-free solder, the molten solder temperature is directly or indirectly through the temperature of the tip 7 closest to the molten lead-free solder. It becomes possible to measure.
Here, as will be described later, the temperature sensor 16 tries to control the time of the cooling process of the molten lead-free solder at the temperature measured by the temperature sensor 16. Therefore, in order to perform this control with higher accuracy, it is preferable that the temperature sensor 16 has a smaller time constant. Specifically, the time constant is preferably 0.1 sec or less, more preferably about 0.01 sec.
Incidentally, many commercially available temperature sensors that are usually used have a time constant of 0.1 sec or more.
In FIG. 1 and FIG. 2, the electric wire attached to the temperature sensor 16 is omitted for the sake of clarity, but this electric wire is led to the outside together with the electric power supply wire to the electromagnetic induction coil 14, A connector 14c is attached to the end.
Then, based on the temperature measured by the temperature sensor 16, while adjusting the amount of the cooling medium flowing from the cooling medium discharge port 15 and the temperature thereof, the temperature of the tip of the tip 7 or the molten solder with which the tip comes into contact is adjusted. The temperature is controlled for a time-temperature while applying ultrasonic waves.

1 and 2, reference numeral 21 denotes a screw 4, a pressing member 5, a piezoelectric element 2, 2, a horn member 3, and substantially the axial center position of the tip portion 7 of the electric iron 1, and the cooling medium discharge port 15. This is a cooling medium flow path communicating with.
Reference numeral 22 denotes a cooling medium delivery pipe that is connected to the cooling medium flow path 21 and feeds a cooling medium such as a cooling gas controlled to an appropriate temperature into the cooling medium flow path 21. Although not shown, there is a tank for storing the cooling medium at the end of the cooling medium delivery pipe 22, and this tank is heated by a heater for heating and the temperature is controlled so that the internal cooling medium is stored. Can be adjusted to a predetermined temperature.
Although only one cooling medium discharge port 15 is shown in the figure, for example, if a plurality of cooling medium discharge ports 15 are arranged radially at predetermined intervals in the radial direction of the distal end portion 7, for example, It is preferable because the tip 7 or the molten lead-free solder can be cooled more uniformly and rapidly.

FIG. 3 is a flowchart showing an example of a control mechanism for controlling the time-temperature of the molten lead-free solder in the electric iron 1 of the present invention shown in FIGS. 1 and 2 while applying ultrasonic waves. is there.
As shown in FIG. 3, in the electric iron 1 described above, when the main switch 20 of the electric iron 1 is turned on, a signal from the temperature sensor 16 attached to the tip 7 of the electric iron 1 is received. A control device (CPU) 30 is entered.
Further, the control device (CPU) 30 sends a signal for controlling the electromagnetic induction coil 14, which is a heater unit, to the heater control unit 40 by a signal from the temperature sensor 16. In conjunction with this, a temperature control signal is sent to the cooling device 50 to heat and cool the cooling medium in the tank to an appropriate temperature, and the flow rate of the cooling medium sent to the cooling medium flow path 21 of the electric iron 1 is adjusted. In addition, a signal for instructing the degree of opening and closing of the valve is also sent to the flow rate adjusting valve 51.

Furthermore, the control device (CPU) 30 also uses the ultrasonic control device 60 that appropriately controls the frequency, amplitude, etc. of the ultrasonic waves generated by the piezoelectric elements 2 and 2 that are the ultrasonic wave generation sources. Correspondingly, an appropriate frequency, amplitude, generation time _Ton or stop time _Toff is indicated each time.
In the present invention, the ultrasonic elements including the horn member 3 that transmits the generated ultrasonic waves to the tip 7 and the ultrasonic control device 60 are transmitted to the piezoelectric elements 2 and 2 that are ultrasonic generation sources. Let's call it a device.

More specifically, the control device (CPU) 30 transmits the ultrasonic generation time T _on , the stop time T _off , and the ultrasonic train pulse generated by the piezoelectric elements 2 and 2 via the ultrasonic control device 60. The generation time Tt _on , the stop time Tt _{off, the} amplitude V, etc. are controlled.
Here, the train pulse is not to generate positive and negative pulses continuously, but to improve the adjustment system of the vibration energy generated by a pulse generation method in which a stop time Tt _off is provided between them. Incidentally, for example, when the electronic component is bonded to the wiring board, this adjustment is performed according to the thickness of the copper film formed on the pad that is the bonding portion on the wiring board side.
Note that each positive and negative pulse may be composed of a plurality of pulses as well as a single pulse.
By the way, the frequency of the ultrasonic wave used in the present invention is 20 KHz to 60 KHz.

Further, a heater portion provided in the distal end 7 of the electric iron 1, that is, when issuing an instruction signal to the electromagnetic induction coil 14 is carried out via the heater control unit 40, the time of occurrence of the load to current T _on, The magnitude of the voltage V is indicated in addition to the stop time _Toff .

Further, the cooling device 50 includes a heater temperature in a cooling gas storage tank built in the cooling device 50 in FIG. 3, or a cooling medium discharged from the cooling medium discharge port 15 via the cooling medium delivery pipe 22 and the cooling medium flow path 21. For example, an instruction about the temperature and amount of the cooling gas is issued.
In the present invention, the time-temperature control device includes the control device (CPU) 30, the heater control unit 40, and the cooling device 50.
Reference numeral 70 denotes, for example, a PC used for inputting control conditions to the control device (CPU) 30 according to the type of lead-free solder used, that is, a personal computer.

With reference to FIG. 4, the specific time-temperature control will be described in detail.
FIG. 4 shows an arbitrary lead-free solder and the above-described electric iron 1 which is an embodiment of the brazing apparatus of the present invention. An example of time-temperature control in the case of joining the connection terminals of the electronic component that is the attachment object is shown.
As shown in FIG. 4, control conditions relating to lead-free solder to be used are input to a control device (CPU) 30 in advance via a PC 70. Then, the main switch 20 of the electric iron 1 is turned on. Then, the control device (CPU) 30 starts time-temperature control of the tip portion 7 of the electric iron 1 while picking up a signal of the temperature sensor 16 attached to the tip of the electric iron 1.

Specifically, as shown in FIGS. 1 and 2, the tip 7 is heated by the electromagnetic induction coil 14 of the tip 7 to raise the temperature of the tip of the electric iron 1. Here, T ₂ is a temperature indicating a freezing point of the lead-free solder used, and T ₁ indicates a melting temperature, that is, a melting point.
When heated and the tip temperature of the electric iron 1 exceeds the melting temperature T ₁ by about 50 ° C. to 200 ° C., that is, the so-called operating temperature Tw, the current flowing through the electromagnetic induction coil 14 by the control of the control device (CPU) 30, While controlling the temperature and amount of the cooling medium discharged from the cooling medium discharge port 15 such as mist-like water or nitrogen gas via the cooling device 50, the tip temperature of the electric iron 1 is set to the operating temperature Tw. return. This state is indicated by reference numeral 80.
When the temperature of the tip 7 of the electric iron 1 is stabilized at the operating temperature Tw, the tip of the electric iron 1 is brought into contact with the lead-free solder, and the lead-free solder is heated and melted.

The tip temperature of the electric iron 1 is temporarily lowered because the heat is taken away by the lead-free solder, but is immediately returned to the operating temperature Tw by the control by the control device (CPU) 30 and the heater control unit 40. This state is indicated by time B. An operator operating the electric iron 1 is watching the state of molten lead-free solder, and judges the time t ₁ (time from B to C) by his / her own judgment, and the heater (electromagnetic induction coil) Turn off the current to 14). That is, heating of the tip 7 of the electric iron 1 is stopped. At the same time the control unit (CPU) 30 starts to monitor the temperature of the signal sent from the temperature sensor 16, when the temperature becomes lower T _D than T _W, immediately through the ultrasonic control unit 60 The piezoelectric elements 2 and 2 are urged to oscillate ultrasonic waves.

The lead-free solder in a molten state reached shortly before the temperature T _E to reach T ₂ is a freezing point, issues an instruction to stop the oscillation of the ultrasonic wave.
The reason why the oscillation is stopped is set to the time E (corresponding to the temperature T _E ) just before the time F (corresponding to T ₂ ) when the lead-free solder in the molten state is completely solidified and solidified. If the ultrasonic wave is continuously applied until the point in time, the tip 7 of the electric iron 1 sticks to the solidified solder, which is to prevent this.
Incidentally, the temperature T _E performs advance several experiments, is determined in advance in terms of played effect of ultrasound addition, moreover the temperature need not surely stuck to the solder solidified the tip of the electric iron 1 .

Here the temperature T _D to promote the oscillation of the ultrasonic wave to the piezoelectric elements 2 and 2 is an ultrasound generating source and composition of the lead-free solder, for example, molten solder which is supplied to the junction of the wiring board and the electronic component The temperature is determined in advance by the amount of. Specifically, if the connection terminal is thick like a power component to the wiring board, and therefore the amount of lead-free solder supplied to the joint is large, small electronic components are joined with lead-free solder of the same composition. as compared with the case, to start the oscillation of the ultrasonic at a lower T _D.

In the present invention, lead-free solder freezing point from the point C by the operator turns off the heater, ie, the time up to the point F to reach the solidification temperature T ₂ - Control of the cooling curve 81 of the temperature is crucial .
The cooling curve 81 is an optimum cooling curve that the lead-free solder has for each composition. The optimal cooling curve here means that the precipitation of the melting point lowering metals such as the main components Sn and Bi is normally performed in the joint, there is no segregation, the crystal grains are fine, and the dispersion is uniform. The cooling curve to be referred to.

It is assumed that the optimum cooling curve 81 that is different for each type of lead-free solder is obtained by experimenting in advance for each type of lead-free solder or corresponding to the amount of solder supplied to the joint.
Therefore, in actual soldering, the control device (CPU) is based on the temperature from the temperature sensor 16 so that the cooling is performed along the cooling curve 81 determined based on the composition of the lead-free solder to be used. 30 performs cooling while controlling the heater control unit 40, the cooling device 50, or the ultrasonic control device 60.
Specifically, the temperature and amount of the inert gas discharged from the cooling medium discharge port 15, the on / off of the heater switch, and the on / off of the piezoelectric element 2 are accurately controlled along the time axis.

In a typical example, assuming that the curve G shown by the solid line in FIG. 5 is the optimum cooling curve 81 of the lead-free solder currently used, the natural cooling curve of the lead-free solder is X If so, the cooling effect is further enhanced, that is, the temperature of the cooling medium supplied from the cooling device 50 is lowered, or the amount of the cooling medium is increased, so that the cooling medium discharge port 15 at the tip of the electric iron 1 is provided. Supply and control to cool more quickly than natural cooling.
On the other hand, when the natural cooling curve of the lead-free solder used is Y, for example, the temperature of the cooling medium to be supplied is slightly increased, and the molten solder becomes more gradual. Control to solidify.
Cooling and control are performed so as to bring the actual cooling curve closer to the optimum cooling curve 81 for the composition of the lead-free solder used in this way.

During the time zone D-E, the above-mentioned time-temperature control is performed while applying ultrasonic waves to the molten lead-free solder from the tip of the electric iron 1. In this case, the lead-free used The ultrasonic control device 60 can control the conditions applied to the piezoelectric element 2 so that an ultrasonic wave having an appropriate frequency, amplitude, and the like can be supplied in accordance with the composition of the solder and the amount of solder supplied.
Here, even if the frequency of the ultrasonic wave is normally controlled, if the electric iron 1 has only one resonance point, the frequency control is practically impossible. Therefore, in advance, it is preferable to form irregularities, specifically grooves and protrusions, at any point of the tip 7 and to make the electric iron 1 have a plurality of resonance points. Alternatively, it is also possible to prepare an electric iron 1 having a tip portion 7 made of a different material and replace the tip portion 7 if necessary.

Furthermore, in the embodiment shown in FIG. 1, only one pair of piezoelectric elements 2 is incorporated. However, a pair of piezoelectric elements 2 that oscillate at different frequencies are incorporated into the piezoelectric element 2 together. It can also be used while switching to a pair of piezoelectric elements or in combination. Here, the various application forms described above are referred to as a resonance frequency correction function.
In this way, even when the heat of the tip 7 is transferred to the piezoelectric element 2 that is an ultrasonic wave generation source and the frequency characteristics thereof are changed, this change can be easily corrected. preferable.

By the way, in general, when ultrasonic waves are applied to molten lead-free solder, the surface tension can be lowered, and as a result, the fluidity of molten lead-free solder increases and wettability is improved. It is said that you can.
Also, it is said that ultrasonic waves improve wettability by destroying the oxide film on the surface of the bonded body. In any case, the wettability of the joint surface is improved by applying ultrasonic waves, and the joint strength between an object such as a wiring board and an object to be mounted such as an electronic component mounted on the object without using any special flux. Can be improved.
In the present invention, the flux may or may not be used. However, as described above, when brazing can be performed without using the flux, there is no possibility that the flux remains in the joint portion. As a result, the possibility that the joint portion deteriorates with time can be reduced. As a result, the long-term reliability of the joint can be further increased. Moreover, deterioration of the working environment due to vaporization of the flux can be prevented.

Further, in this cooling step, it is preferable to surround the molten lead-free solder with a wall or the like so as to block it from the outside so that cooling with a cooling medium such as cooling gas can be performed more efficiently and accurately. . In this way, even when an expensive cooling gas is used, the amount of use can be reduced, which is also preferable in this respect.
As described above, in the cooling process of molten lead-free solder, when ultrasonic waves are applied and time-temperature control is performed at the same time, Sn as the main component of lead-free solder, as well as Bi When such a melting point lowering metal is added, segregation including this melting point lowering metal can be prevented, and a bonded portion having a fine crystal grain and a uniform distribution can be obtained.
As a result, when lead-free solder is bonded, a bonding portion with high bonding strength, little variation, and high reliability over a long period can be obtained.

In order to confirm the difference between the brazing method according to the present invention and the brazing method disclosed in Patent Document 1, an electronic component is soldered to a wiring board using Sn-3.5Ag which is a typical lead-free solder. did. When the cross section of the junction part obtained in that case was observed with the electron microscope, both had the following differences.
That is, both the method of the present invention and the method disclosed in Patent Document 1 are sufficient for the alloy layer formed between the copper pad of the wiring board and the solder, and could not find much difference. A clear difference was observed in the size and distribution of Sn crystal grains in the solidified solder layer.
Specifically, according to the method of the present invention, the size of Sn crystal grains was clearly smaller than that obtained by the method described in Patent Document 1, and segregation was also small. That is, the size of the Sn crystal grains was smaller and the distribution thereof was remarkably uniform in the joint obtained by the method of the present invention.
As a result, the connection strength was higher in the present invention and the variation was small.

In FIG. 1, when the horn member 3 is formed of a material having excellent heat insulation, such as titanium, stainless steel, glass, porcelain, or a combination thereof, the heat of the tip 7 of the electric iron 1 is an ultrasonic wave generation source. It becomes difficult to exert an influence on the piezoelectric elements 2 and 2, and the thermal influence on the ultrasonic wave can be more reliably eliminated.
Alternatively, a similar effect can be obtained by interposing this type of heat insulating material in a part of the horn member 3 in the axial direction, specifically, at both ends of the horn member 3 or at any position in the axial direction.
Specifically, the horn member 3 is cut perpendicularly to the axis of the horn member 3 at a position closer to the left end face 3a in FIG. 1, for example, at a cut position, for example, titanium, stainless steel, glass or What is necessary is just to interpose the heat insulation member of the appropriate thickness which consists of porcelain etc.
In this case, the shape and size of the heat insulating member to be interposed are the same shape and the same size as the contact surface of the horn member 3 that is in contact therewith, and the contact surfaces of the heat insulating member and the horn member 3 are mirror-finished and adhered. It is preferable. When the heat insulating member is interposed as described above, the influence on the ultrasonic wave generation source due to the heat of the electromagnetic induction coil 14 can be minimized.

In the brazing method of the present invention described above, only the embodiment using an electric iron is shown, but the brazing method of the present invention can be applied to, for example, a reflow furnace.
Moreover, although only the electric iron which employ | adopted the induction heating system was shown as the brazing apparatus mentioned above, it cannot be overemphasized that the electric iron which hold | maintained the normal heater inside the front-end | tip part 7, for example may be sufficient. .
In the embodiment, the temperature of the molten solder is directly or indirectly measured by the temperature sensor 16 attached to the tip of the electric iron 1, and the cooling process of the molten solder is ultrasonicated. In addition to this, time-temperature control is performed.In addition to this, the surface temperature of the molten solder is measured using an infrared temperature sensor, etc., and the time-temperature control of the cooling process can be performed at this temperature. it can.

Further, in the embodiment, the tip portion 7 of the electric iron 1 is formed by applying a coating layer 18 such as iron plating, which is a magnetic body, to the copper main body portion 12. It is made of iron of 0.1 mm or more or made of iron / nickel alloy, the outer shape is bullet-shaped as shown in FIGS. 1 and 2, and is different from that of FIGS. Even if the tip 7 is formed of a container-like member, it can be excited by the electromagnetic induction coil 14 formed by winding the electric wire 13 and can generate heat necessary and sufficient as an electric iron.
Moreover, although only the embodiment example of a copper conductor is shown as a conductor of the electric wire 13, this can also be formed with a nichrome wire. In this case, there exists an advantage which can always hold | maintain the front-end | tip part 7 of the electric iron 1 in the preheating state with the Joule heat which self generate | occur | produces.

  Although not described in the above embodiment, when the present invention is applied to, for example, soldering between a wiring board and an electronic component mounted thereon, the periphery of the wiring board is covered with a wall material, or the wiring board If the work is performed by covering only the periphery of the electronic components actually mounted with a wall material, the time and temperature of the molten brazing material can be controlled more quickly and accurately, and at the same time the cooling range is narrow. As a result, it is possible to reduce the amount of the cooling medium used.

  As described above, according to the present invention, even when lead-free solder is used, for example, the bonding strength between a mounted object such as a wiring board and a mounted object such as an electronic component mounted thereon is high. In addition, it is possible to provide a brazing method and a brazing apparatus that employs this brazing method with a long-term reliability with little change in bonding strength over time.

It is a partial cross section schematic front view which shows the principal part of the electric iron which shows one embodiment of the brazing apparatus of this invention. It is a partial cross-section enlarged view of the front-end | tip part of the electric iron shown in FIG. FIG. 2 is a flowchart showing an embodiment example for time-temperature control of a molten lead-free solder cooling step performed using the electric iron shown in FIG. 1 while applying ultrasonic waves. One embodiment of time-temperature control when using an arbitrary lead-free solder and using the electric iron shown in FIGS. 1 and 2 and joining an electronic component to a wiring board while applying ultrasonic waves It is a flowchart to show. It is a graph which shows the relationship between the optimal cooling curve and natural cooling curve in arbitrary lead-free solder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric iron 2 Piezoelectric element 3 Horn member 7 Tip part 13 Electric wire 14 Electromagnetic induction coil 15 Cooling medium discharge port 16 Temperature sensor 17 Main body 18 Cover layer 20 Main switch 21 Cooling medium flow path 22 Cooling medium delivery pipe 30 Controller (CPU) )
40 Heater control unit 50 Cooling device 60 Ultrasonic control device

Claims (6)

In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
A brazing device having a function of increasing the peel strength of brazing. In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
Reduce the diameter of the crystal particles of the brazing material that has been cooled and solidified,
And / or
By homogenizing the dispersion of crystal particle diameters,
A brazing device having a function of increasing the peel strength of brazing. In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
Reduce the number of voids per unit volume in the cooled and solidified brazing material,
And / or
By reducing the average diameter of the voids,
A brazing device having a function of increasing the peel strength of brazing. In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
By improving the wetting properties of the molten brazing material on the surface of the brazing material,
A brazing device having a function of increasing the peel strength of brazing. In a brazing device that cools and solidifies the brazing material on the surface of the brazing material after the brazing material is heated and melted,
For brazing filler metal melted by heating,
During the period when the brazing filler metal in the cooling process after heating is in a molten state,
By irradiating the brazing filler metal in the molten state with ultrasonic waves,
Compared to the case where no ultrasonic wave is irradiated during the period,
A brazing material surface;
At the interface with the brazing material in the molten state and / or the cooled and solidified state,
By forming an alloy layer of brazing material and brazing material,
A brazing device having a function of increasing the peel strength of brazing. The brazing material is a lead-free brazing material,
The brazing apparatus according to any one of claims 1 to 6.